There are Thai employment agencies who find staff for such work, which, like everything else, can be searched and contacted online (by your Thai wife if in Thai). My Thai partner (while Im in the UK), has found live-in work in BKK as a nanny/housekeeper with a wealthy Chinese family through such an agency. She also has a friend who lives in and cares for an elderly lady, now bedridden, with Dementia. For this work (dementia) I would think the right attitude and disposition would be more important than being medically trained.